“Apparatus for magnetically deployable catheter with MOSFET sensor and method for mapping and ablation,” U.S. Pat. No. 7,869,854, filed on Feb. 23, 2006, published as U.S. Pat. Application No. 2007/0197891, assigned to Magnetecs Corporation, which discloses a MOSFET sensor guided by a magnetically-deployable mechanism, is incorporated herein by reference. Corresponding applications include EPO Patent No. 07751190.5; Canadian Patent No. 2637622; and Hong Kong Patent No. 09104053.7.
Nevertheless, there is a great and still unsatisfied need for an apparatus and method for measuring biopotential activity with the use of a MOSFET sensor. This application further improves the efficacy and safety of the procedure by enabling an accurate disclosed method and apparatus which provides for high fidelity sensing of the nerve bundle electrical activity which has a direct measure to the outcome of the procedure efficacy and safety.
The art of electrophysiology studies employs variety of devices, specifically catheters with different electrical configurations of electrodes using magnetic as well as electrical impedance technique to form an electro-anatomical map. Because of its high success rate and low morbidity, radiofrequency (RF) catheter ablation has become a first line treatment for many arrhythmias. In this procedure, one or more electrode catheters are advanced percutaneously through the vasculature to contact cardiac tissues. Radiofrequency energy of up to 50 W for 60 seconds is delivered so as to remodel the electrical path or circuit within the heart chamber.
However, ablation of more complex arrhythmias, including some atrial tachycardias, many forms of intra-atrial re-entry, most ventricular tachycardias, and atrial fibrillation, continues to pose a major challenge. (Paul A Friedman Heart. 2002 June; 87(6): 575-582). This challenge stems in part from the limitations of fluoroscopy and current napping catheter construction and sensory apparatus to locate accurately both the geometry and time domain of the wavefront activity generated by the “avalanche” of the cellular excitable matrix. The inability of the current electrode technology to account for the cellular biopotential transfer with the resolution and the ionic transfer time depicting the actual energetic event is insufficient in the measurement as well as representing the “avalanche” dynamics of this bioenergetic event. This is the main drawback of the existing and prior art relating to “electrode technology”.
The drawback noted above, whereby the existing art does not account for the dynamics of the ionic potential with the necessary fidelity which mimics the actual energetic event, is further supported by the use of the “conductor geometry” theory, which represents the cellular path as a cable i.e.: “the cable theory”, or the mathematical modeling of bioelectrical current along passive neuronal fibers. Existing hardware employing electrode technology, coupled with the general algorithmic representation of the biopotential dynamics under such theory (both hardware and cable theory) suffer from the limitations which the invention disclosed below solves by the use of the MOSFET sensor array and its method of map reconstruction, as shall be annotated by the figures and their associated description.
In summary, the problem of reconstruction of the electrophysiological activity in the prior art is two-fold: At the one hand it is the results of the use of electrodes and its associated electrical circuit design, and on the other hand it is further handicapped by modeling the biopotential activity as a physical phenomenon whereby excitable cells are modeled by employing the “cable theory” with isotropic behavior. The use of electrodes and cable theory is a good approximation of idealized conditions of such energetic events, but suffers from the inability to associate accurately the intracardiac electrogram with a specific endocardial site which also limits the reliability with which the roving catheter tip can be placed at a site that was previously mapped. This results in limitations when the creation of long linear lesions is required to modify the substrate, and when multiple isthmuses or “channels” are present. Additionally, since in conventional endocardial mapping a single localization is made over several cardiac cycles, the influence of beat-to-beat variability on overall cardiac activation cannot be known.
The need to improve modeling of cellular electrical activity is central to physiology and electrophysiological studies. Biopotential recording and mapping of such electrical activity enables the physician or researcher to form and fashion his or her understanding of the fundamental data gathering and analysis of such diverse biological activities as sensory perception, communication between neurons, initiation and coordination of skeletal-muscle contraction, synchronization of the heart beat, and the secretion of hormones.
Most mathematical models of cellular electrical activity are based on the cable model, which can be derived from a current continuity relation on a one-dimensional ohmic cable. As such, its derivation rests on several assumptions: ionic concentrations are assumed not to change appreciably over the time of interest, and a one-dimensional picture of cell geometry is assumed to be adequate for purposes of describing cellular electrical activity. These assumptions, however, may not hold in many systems of biological significance, especially in the central nervous system and cardiac tissue, where micro-histological features may play an essential role in shaping physiological responses.
The invention and its embodiments, as featured by the use of an integrated MOSFET Sensor Array, solves this and other problems of local definition of reporting on essential electro-physiological parameters, without the compromise noted the prior art, some of which are described by Bin Yin et al US Pat. Pub. 2011/0137200, which describes a system and a method in which an electrophysiological signal is sensed capacitively with at least two closely spaced electrodes such that the electrodes experience strongly correlated skin-electrode distance variations.
Chii-Wann Lin et al in US Pat. Pub. 2010/0145179, describes a high-density micro-electrode array connected to the same conducting wire. Serial switches enable sequential electrical connection of the micro-electrode array.
Paul Haefner in US Pat. Pub. 2007/0293896 describes an arrhythmia discrimination device and method which involves receiving electrocardiogram signals and non-electrophysiological signals at subcutaneous locations. Both the electrocardiogram signals and non-electro physiologic signals are used to discriminate between normal sinus rhythm and an arrhythmia.
These methods have limited success in reaching and reporting on an electro-anatomical site and reduces the ability of the operator to provide a clinically optimal resolution to the problem of identifying accurately the source and its location and further, the prior methods and their exemplified apparatus cannot achieve such precision, and hence results in suboptimal successes of remodeling the heart electrical signal propagation, as well as neuromodulation and their intended clinical outcomes.